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 1 

Proceedings of the 1st Rail Transportation Division Fall Technical Conference 

RTDF2007 

September 11-12, 2007, Chicago, Illinois, USA 

RTDF2007-46015 

DEVELOPING STRATEGIES FOR MAINTAINING TANK CAR INTEGRITY DURING 

TRAIN ACCIDENTS 

David Tyrell 

Karina Jacobsen 

Brandon Talamini 

Michael Carolan 

Volpe National Transportation Systems Center 

Cambridge, Massachusetts, USA 

ABSTRACT 

Accidents that lead to rupture of tank cars carrying 

hazardous materials can cause serious public safety hazards and 

substantial economic losses. The desirability of improved tank 

car designs that are better equipped to keep the commodity 

contained during impacts is clear. This paper describes a 

framework for developing strategies to maintain the structural 

integrity of tank cars during accidents. 

The target of this effort is to design a tank car capable of 

surviving impacts without loss of lading at twice the impact 

speed of current equipment (or, equivalently, is capable of 

absorbing four times the impact energy). The methodology 

developed breaks down the process into three steps: 

1. Define the impact scenarios of concern 

2. Choose strategies to mitigate failure modes 

present in each scenario 

3. Design and select technology and tactics to 

implement the mitigation strategies 

The railroad accidents involving tank cars that occurred in 

Minot, ND, in 2002, and Graniteville, SC, in 2005, are 

examined to define the impact scenarios. Analysis of these 

accidents shows that two car-to-car impact scenarios are of 

greatest concern: head impact, where railroad equipment 

impacts the end of a tank car and possibly overrides it, and 

shell impact, where the tank car is impacted on its side, 

possibly off center. 

A conceptual design that can protect its lading at twice the 

impact speed of current equipment in the car-to-car impact 

scenarios is being developed. The conceptual design includes 

four functions to meet the impact requirements: blunts the 

impact loads, absorbs collision energy, strengthens the tank, 

and controls the load path to assure that loads are blunted and 

that energy is absorbed before the tank is loaded. 

Preliminary studies of available weight and space, 

strategies for increasing energy absorption, and strategies for 

strengthening the head and shell are ongoing; this paper 

describes the current results of these studies. Additional studies 

are also ongoing. The steps required to complete this effort are 

also described. 

INTRODUCTION 

In support of the Federal Railroad Administration (FRA), 

the Volpe National Transportation Systems Center (Volpe 

Center) is conducting research on improving tank car safety. 

The results of this research are being used to help form the 

technical basis for ongoing tank car safety rulemaking, which is 

being carried out by the Pipeline and Hazardous Material 

Safety Administration (PHMSA) and FRA. This rulemaking 

activity is focused on tank cars which carry materials that are a 

Toxic Inhalation Hazard (TIH), such as chlorine. This research 

is intended to support the activities described in a press release 

issued by FRA on January 16, 2007 [1]: 

“Our goal is to jump beyond incremental design changes,” 

[FRA Administrator Joseph H.] Boardman said. “We and our 

partners are looking to apply the latest research and advanced 

technology to provide increased safety for rail shipments 

posing the greatest safety risk,” he explained, noting that FRA 

is considering issuing new, more robust Federal design 

standards for hazardous materials tank cars and hopes to issue 

a final rule in 2008. 

The goal set for this research is to double the car-to-car 

impact speed for which integrity of the tank can be maintained 

and the commodity contained. This paper describes one aspect 

of the tank car safety research—the development of an 

improved conceptual design. The purpose of the conceptual 

design is to show that the chosen goal can be met. Results 

from the development of the improved conceptual design are 
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 2 

being used to estimate benefits and costs, demonstrate 

techniques for evaluating compliance with selected 

requirements, and exemplify technologies needed to increase 

tank integrity in accidents. Companion papers describe other 

aspects of this research, including full-scale testing of the 

baseline equipment [2], material failure modeling [3], train 

collision dynamics modeling [4], and an overview of the entire 

research effort in support of the PHMSA and FRA rulemaking 

activity [5]. While significant progress toward the goal has 

been made, the research is not yet completed. 

APPROACH 

The approach used in conducting this research is illustrated 

in the flow diagram shown in Figure 1. 

1. Define the collision scenarios of concern. The 

accidents identify the conditions for which the 

commodity is to be contained. These conditions 

include the collision or derailment speed, the train and 

other objects, and the track conditions [4, 6]. The goal 

in developing the collision scenarios of concern is to 

develop a limited number of scenarios that bound the 

range of conditions leading to loss of lading. These 

scenarios are used as the basis for evaluating the 

effectiveness of alternative tank car designs. 

2a. Develop information on the features of existing 

designs that influence crashworthiness. Information on 

the design details of the equipment—the geometry of 

the structure, material properties, welding and 

attachment details—are developed for use in analytic 

models and in the development of test articles [7, 8]. 

2b. Develop potentially improved designs. A clean-sheet 

design is being developed. The functions and features 

of the clean-sheet design are also being evaluated to 

determine if they can be incorporated into existing 

designs. This paper focuses on this aspect of the 

research. 

3. Evaluate the effectiveness of existing design and 

potentially improved design equipment. From postaccident results, it can be seen how effective the 

equipment was in containing the commodity. Gaps 

and uncertainties exist in the information available 

from accidents. Analyses and tests are used to fill in 

these gaps [2, 3, 5, 6, 7, and 8]. Analytic models and 

tests, similar to those developed and conducted for the 

conventional equipment, are used to evaluate the 

effectiveness of the alternative designs. 

4. Compare the effectiveness of the alternative designs 

with the existing designs. For a given accident 

scenario of concern, comparisons are made in terms of 

the maximum collision speed for which the 

commodity would be contained. 

5. In order to evaluate the crashworthiness of existing 

and alternative designs, analytic tools and testing 

techniques are developed and refined. Accidents 

provide information for comparison to analytic model 

predictions and help provide some level of assurance 

of the fitness of the models. Much is often unknown 

about an accident, such as the precise collision speed 

and exact initial conditions for the equipment. Testing 

provides more detailed information for comparison 

with analysis predictions [2]. 

Develop 

Scenarios Evaluate

Compare 

Effectiveness 

of Potentially 

Improved and 

Existing 

Designs

Existing 

Equipment 

Designs

Modeling 

and 

Testing

Potentially 

Improved 

Designs

Revise

1

2a

3

4

5

2b

Figure 1. Flow Diagram, Tank Car Safety Research 

Principal Tasks 

This approach has been successfully applied to several 

research projects in the area of rail equipment crashworthiness. 

Examples include development of crush zones (referred to as 

crash energy management or CEM) for passenger equipment 

[9, 10, 11], a state-of-the-art cab car end frame [12] for 

preserving the operator’s space, an improved workstation table 

for limiting abdominal injury [13], and an optimized commuter 

seat design [14] for protecting both rear and forward facing 

passengers. Concepts developed with this approach include 

deformable locomotive short hood and collision posts [15] for 

preserving the operator’s space and inflatable structures for 

locomotive operator protection [16]. 

IMPROVED DESIGN DEVELOPMENT 

Collision dynamics and structural response, as well as 

material failure are the tools used in the design development. 

The collision dynamics determine how the loads are applied to 

the structure. The structural response, in combination with the 

collision dynamics, determines the magnitude of the loads. For 

a given impact speed, if the structure is relatively soft, then the 

impact loads will remain low; if the structure is relatively stiff, 

then the loads may become large. The magnitude of the load in 

combination with the structural response and material 

properties determines if material failure occurs. For a given 

material and load, material failure may occur with an impacting 

object that focuses the load on the tank, while material failure 

may not occur for an impacting object that disperses the load 

on the tank [3]. 

Figure 2 shows a flowchart of the process for developing 

the improved tank car design. The design requirements 

describe the desired performance of the tank car in detail. 

Using these, concepts for meeting the requirements were 

generated, rated, ranked, and selected. Preliminary design 
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 3 

studies to support the refinement of the selected concept are 

ongoing. This paper describes the selected design concept, as 

well as results from preliminary design studies. 

Generation of 

Alternative 

Concepts

Concept 

Selection

Rating and 

Ranking of 

Concepts

Preliminary 

Design 

Studies

Design Goals

Identify and 

organize 

concepts

Assess 

concepts’

potential for 

meeting 

requirements

Choose 

concept with 

most potential

Develop 

concept details

Service, Manufacturing, 

Crashworthiness,

etc.

Figure 2. Design Development Process 

Key Design Requirements

The design requirements for all of the conventional 

aspects—service, manufacturing, inspection, test, and 

maintenance—do not vary substantially from the current 

requirements for conventional tank cars. The greatest 

difference is in the crashworthiness requirements. 

Requirements have been added that prescribe how the tank car 

must perform in selected impact conditions. 

Figure 3 is a schematic of the head impact design 

requirement. The tank car must be able to retain its lading for 

an impact with a rigid fixed punch with a blunt end. The 

impact occurs below the tank’s centerline. The goal is to 

increase the amount of impact energy for which the tank can 

contain the commodity by a factor of four. Meeting this goal 

would double the impact speed for which the integrity of the 

tank can be maintained. 

Tank Car

Elevation View

Plan View

V

V

Tank Car

Punch

Figure 3. Schematic of Head Impact Requirement 

Figure 4 is a schematic of the shell impact design 

requirement. In this scenario, the side of the tank car is 

impacted by a ram car with a blunt punch. The impact occurs 

at the tank’s centerline. The improved tank car must be able to 

retain its lading for an impact with four times the energy as the 

impact for which the baseline tank car can retain its lading. As 

for the head impact design requirement, meeting this goal 

would double the impact speed for which the integrity of the 

tank can be maintained. As described in the references [2 and 

3], the speed for which tank integrity is maintained depends on 

the height and width of the nose of the blunt punch. The 

relative increase in performance sought is the same for a wide 

range of nose sizes. 

Ram Car Tank Car

Punch

Tank Car

Ram Car

Elevation View

Plan View

X2 mph

X2 mph

Figure 4. Schematic of Shell Impact Requirement 

Figure 5 for the shell impact illustrates the connection 

between speed and the energy the tank car must be able to 

absorb without loosing its lading. The initial kinetic energy of 

the moving equipment is translated into the work done to 

elastically and plastically deform the structure. These impact 

requirements drive the design differences between the 

improved design and conventional design tank cars. 

Figure 5. Initial Kinetic Energy and Energy Absorbed by 

Tank Car in Shell Impact 
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Selected Concept

Aspects of the conceptual design include how the design is 

intended to function and what features are included to perform 

these functions. The functions are qualitative descriptions of 

how the car structure is intended to behave in the selected 

impact scenarios. The design features are intended to perform 

the desired functions. The form is the realization of a design 

with these features and functions, which would be a 

constructible design. Several iterations of a constructible 

design, with component tests and associated analyses, may be 

necessary before a final production design is developed. 

Table 1 lists the functions and associated features of the 

selected concept. The conceptual design must perform the 

following four functions to meet the impact requirements 

associated with head and shell impact scenarios: blunt the 

impact loads, absorb collision energy, strengthen the tank, and 

control the load path to assure that loads are blunted and that 

energy is absorbed before the tank is loaded. 

Table 1. Conceptual Design Functions and Features 

Reinforcement of head and 

shell

Strengthened tank

Carbody supports service 

loads

Sacrificial structure that 

shields tank and absorbs 

energy

Features

Controlled load 

path to tank

Collision energy 

absorbed

Blunted impact 

loads

Functions

Reinforcement of head and 

shell

Strengthened tank

Carbody supports service 

loads

Sacrificial structure that 

shields tank and absorbs 

energy

Features

Controlled load 

path to tank

Collision energy 

absorbed

Blunted impact 

loads

Functions

Blunt Impact Load

Head shields on current cars principally act to blunt the 

impact load. The shield makes the size of the impacting object 

appear larger to the tank, spreading the load over a greater area, 

and makes any sharp edges appear to have a larger radius, 

dispersing the stress in the tank. By doing so, the energy 

required to rupture the tank is increased. The concept is to 

include a feature which can blunt the impact load on any part of 

the tank, that is, to cover the entire tank with a shield. Figure 6 

illustrates the functioning of such a shield. 

Tank

Tank

Head Shield

Figure 6. Schematic Illustration of a Head Shield Spreading 

Load and Dispersing Stress 

Absorb Collision Energy

The addition of an energy absorption component between 

the shield and the tank can further increase the energy required 

to rupture the tank. In essence, the energy absorption layer 

decreases the speed of the impact experienced by the tank. The 

energy absorption layer can significantly slow down the 

impacting object before the tank is significantly loaded. Figure 

7 illustrates the combined functioning of a shield and energy 

absorption component. 

Tank

Tank

Energy Absorbing Material

Figure 7. Schematic Illustration of Combined Head Shield 

and Energy Absorption Component Function 

Strengthen Tank

Strengthening the tank allows an energy absorption 

component to crush at a higher load. As suggested by Figure 5, 

the higher the load required to deform the tank car (and its 

components), the more energy required to rupture the tank car. 

Since the head can ‘snap through’ at a relatively low load [7], 

the energy absorption crush load that can be supported without 

reinforcement is relatively low. Similarly, the shell tends to 

ovalize and dish at a relatively low load when impacted [2], 

limiting the amount of energy that can be absorbed without 

reinforcement. 

If the tank remains the main service load bearing structure, 

then the potential for weldments to lead to fatigue failures is of 

concern. In such a case, bonding the reinforcement to head and 

shell is a potential option. If the service load bearing structure 

is separate from the commodity tank, and the tank does not 

experience cyclic service loads, then the potential for fatigue 

failure is much lower. In such a case, directly welding to the 

head and shell may be a viable option. 

Load Path

Accident history suggests that rupture can initiate 

anywhere on the tank. Ruptures are more likely at certain 

locations on the tank—below the belt line and at the ends of the 

car. However, cars appear to have been ruptured owing to 

impacts near the draft sill/body bolster and on the top. These 

accident results suggest that the entire car should be shielded 

and that collision energy should be absorbed before the tank is 

impacted. In order to accomplish this function, a separate 

carbody structure supports the service loads. 
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Integrated Design

Figure 8 shows a schematic of the features integrated into a 

conceptual design. Potentially, these features could be applied 

incrementally to existing designs, working from the inside out. 

The tank could be strengthened with bonded stiffeners alone. 

As described in the preliminary design study section of this 

paper, such stiffeners have the potential to double the energy 

required to rupture the tank. A sacrificial structure for blunting 

the load and absorbing energy could be further added. The 

tank stiffeners and sacrificial structure together could increase 

the energy required to rupture the tank by a factor of four. 

Such a car would be at least somewhat more vulnerable near 

the draft sill/body bolster attachments, even if these 

attachments act as structural fuses and fail in a prescribed 

manner for prescribed loads. Impact loads that bypass the 

sacrificial structure could be introduced to the tank through the 

Achilles’ heel of the draft sill/body bolster. The external 

carbody would eliminate this vulnerability and result in the 

integrated conceptual design. For example, the continuous 

center sill design relieves the tank from bearing the in-train 

buff and draft forces and continues to be used in DOT 

105A500W tank cars built for carbon dioxide service. 

Sacrificial Structure

Blunt Force and Absorb Energy

Carbody

Carry Service Loads

Reinforcement

Strengthen Tank

Design Integration

Service, Manufacturing, and Crashworthiness Goals

Figure 8. Schematic Illustration of the Integrated 

Conceptual Design 

PRELIMINARY DESIGN STUDIES 

Preliminary studies of available weight and space, 

strategies for increasing energy absorption, and strategies for 

strengthening the head and shell are ongoing. Managed energy 

absorption is necessary to achieve improvements in tank car 

crashworthiness. Weight and space are primary constraints on 

energy absorption features. The collapse strength of the 

support structure is also a constraint on energy absorption 

features. The stronger the tank, the greater the load that the 

energy absorbing structure may crush at, and the smaller the 

crush distance required for a specified amount of energy 

absorption. 

This section describes the current results of the preliminary 

design studies. Only the results for the head impact scenario 

are described. Parallel results have been achieved for the shell 

impact scenario. Studies on additional design details of the 

sacrificial structures, including means of blunting the load and 

of the carbody structure, are also ongoing. The results of the 

preliminary design studies will be described in follow-on 

papers once the studies have been completed. 

Weight and Space

In order to achieve adequate performance of a new car 

design, it may be necessary to change the shape and size of the 

tank car. Such changes could result in issues related to how the 

commodity is loaded and unloaded. Some facilities will have 

to re-evaluate the top platform design in order to access the top 

fittings. If multiple cars are loaded/unloaded at one time, then 

car spacings where such fixtures are located will need to be 

evaluated, perhaps requiring some to be redesigned. 

Additionally, it is understood that the design must account for 

placement of safety appliances. The details of the final car 

layout will be defined in the next phase of design development 

and discussed in future work. 

The baseline car chosen for this study is a DOT 105J500W 

car, the same class of tank car used in the full-scale crash tests 

[2]. This baseline car is constructed to Association of 

American Railroads (AAR) plate B clearance standards [17]. 

The clearance standard dictates the maximum car height, 

width, and truck center spacing for compliant cars. For plate B, 

the maximum allowable height of any portion of the car is 15’-

1” above top-of-rail. At the maximum allowable width of 10’-

8”, truck centers cannot exceed 41’-3”. Figure 9 shows the 

envelope for equipment built to plate B. 

Top of rail

15’-1”

10’-8” 41’-3”

(truck to truck)

Figure 9. Maximum Dimensions for Plate B 

For a car with the maximum distance between truck 

centers, the length of structure outboard of the trucks must also 

be considered in the car’s design. The swingout at the ends of 

the car cannot exceed the swingout at the center of the car on a 

13o

 curve [17]. A car built to plate B with maximum distance 

between truck centers has a swingout at the center of the car of 

5 3⁄4”. By extending the length of the car outboard of the trucks 

until this same swingout is achieved at the end of the car, a 

maximum overall car length of 57’-10” can be achieved. 

The baseline car’s tank has an outer diameter of 8’-6 3/10” 

and a nominal capacity of 17,300 gallons. This tank has a 1’- 
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 6 

7/8” clearance on either side before encountering the maximum 

allowable car width. This clearance effectively limits the 

maximum amount of energy absorbing material that can be 

placed around the tank. As illustrated in Figure 5, increasing 

the thickness of material being crushed at a given force will 

result in more energy being absorbed.

Since the clearance diagram width cannot be extended, the 

only way to include more space for energy absorbing material 

around the tank’s circumference is to decrease the tank’s 

diameter. Figure 10 shows a tank with a diameter 5” less than 

the baseline overlaid on the baseline tank. The tank length has 

been extended to maintain the same volume as the baseline 

tank. With a head-to-head length of approximately 48’, 

sufficient clearance exists for placement of new structure 

surrounding the head. 

Figure 10. Baseline Tank and Reduced Diameter Tank 

One concern associated with the addition of new structure 

to the car is the additional weight that this will contribute. For 

the improved crashworthiness tank car, the maximum allowable 

weight is 286,000 lb. The new design includes many of the 

same features of a conventional tank car, including the tank 

assembly, truck assemblies, safety appliances, and an equal 

lading capacity of 90 tons of chlorine. In addition, the new 

design will include a strengthened tank, energy absorbing 

material, and a structural frame to bear the service loads. 

Table 2 shows the weights of components common to both 

conventional and improved crashworthiness tank cars. These 

preliminary values are given to estimate the amount of weight 

that is available for new structure. Based on the weights of 

existing tank car components and the 286,000 lb limit, 

approximately 39,000 lb are available for new structure. This 

available weight comes from increasing the car weight and 

from incorporating the functions of the baseline car’s jacket 

and the stub sill/body assemblies into alternative components. 

Table 2. Weight Breakdown of Tank Car Components 

Weight (lbf)

Bare Tank (t = 0.777") 38280

Truck Assemblies (2) 20580

Coupler/Draft Gear Assemblies (2) 2300

Air Brake Assembly 1310

Fittings and Housing Assembly 1300

Manway 1300

Ladders/Handholds/Railings 1100

Handbrake Assembly 420

Paint/Markings 100

Chlorine 180000

Subtotal 246690

Available for new structure 39310

Target Energy Absorption and Kinematics

The crashworthiness performance of a tank car is defined 

by its ability to maintain tank integrity for a given impact 

condition at a minimum speed. Figure 5 illustrates the 

relationship between the collision speed in the shell collision 

scenario and the energy absorption requirement for a tank shell 

to maintain tank integrity. For the baseline tank shown in 

Figure 11, the shaded area under the force-indentation curve up 

to the point of possible rupture represents the energy absorption 

required for the head to maintain tank integrity. The tank car 

research goal is to increase the collision speed for which tank 

car integrity can be maintained by a factor of two. An 

improved tank car that can withstand twice the speed will have 

energy absorption requirements four times that of the baseline 

tank car. 

Ebs ~ 1 million ft-lb

0

500

1000

1500

2000

2500

0 5 10 15 20 25 30 35 40 45 50

Dent (in)

Force (kip)

0

500

1000

1500

2000

2500

0 5 10 15 20 25 30 35 40 45 50

Dent (in)

Force (kip)

Rupture 

possible

Figure 11. Idealized Force-Indentation Characteristic for a 

Conventional Head 

Figure 12 illustrates the desired kinematic sequence of the 

conceptual design tank car for the head impact requirement. 

The conceptual design includes the crashworthiness features 

described in Table 1 and illustrated in Figure 8. By designing a 

tank car to crush in the prescribed sequence shown, the 

collision unfolds in a more predictable and controlled manner. 

For the head scenario, in state 1, initial contact is made between 

the indenter and the outer tank carbody. In state 2, a sacrificial 

energy absorbing layer begins to collapse. The footprint of the 
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 7 

indenter is spread over a wider area; by state 3, a less severe 

and more distributed load is applied to the commodity tank. In 

state 4, the head deforms until rupture occurs in state 5. 

1

2

3

State

5

4

Initial Punch Contact with Carbody

Energy Absorbed by Crushable 

Structure

Crushable Structure Collapses, 

Contact with Head

Head Crushes

Head Ruptures

Figure 12. Head Impact Scenario: Improved Tank Car 

Target Kinematic Sequence of Events 

Figure 13 shows the energy absorption requirements of an 

improved design. The desired force-indentation characteristic 

was developed using the space constraints addressed earlier in 

this paper and the features identified in Table 1. The resultant 

curve represents an improved tank that has a sacrificial 

structure that absorbs energy and distributes the load applied to 

a strengthened head. 

Figure 13. Head Force-Indentation Characteristics 

A desired kinematic sequence for the conceptual design 

tank car in a shell impact and a target force-indentation 

characteristic for the shell have also been developed. Figure 14 

illustrates the shell kinematic sequence, and Figure 15 shows 

the target force/indentation characteristic. The desired 

kinematic sequence for the shell impact parallels that for the 

head impact. In state 1, initial contact is made between the 

indenter and the outer tank carbody. In state 2, a sacrificial 

energy absorbing layer begins to collapse. The footprint of the 

indenter is spread over a wider area, and by state 3, a less 

severe and more distributed load is applied to the commodity 

tank. In state 4, the head deforms until rupture occurs in state 

5. 

1

2

3

State

5

4

Initial Punch Contact with Carbody

Energy Absorbed by Crushable 

Structure

Crushable Structure Collapses, 

Contact with Shell

Shell Crushes

Shell Ruptures

Figure 14. Shell Impact Scenario: Improved Tank Car 

Target Kinematic Sequence of Events 

Figure 15 shows force-indentation characteristics for the 

baseline tank, a tank with an energy absorbing structure added, 

and a reinforced tank with an energy absorbing structure. 

Adding just an energy absorbing structure to a baseline shell 

can potentially increase the energy for which tank integrity is 

maintained by a factor of 2, increasing the speed for which tank 

integrity is maintained by 50 percent. Further, strengthening 

the shell and adding an energy absorbing layer potentially 

increases the energy for which tank integrity is maintained by 

four and doubles the speed for which tank integrity is 

maintained. 

Figure 15. Shell Force-Indentation Characteristics 

Design studies to determine how to achieve the desired 

kinematics and the target force-indentation characteristics for 

the head and shell are ongoing. If structures that meet these 

design goals can be developed, then an improved tank car can 

meet the impact conditions illustrated in Figures 3 and 4. 

Head Strengthening

As illustrated in the previous section, the capacity of the 

energy-absorbing components may be extended by increasing 
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 8 

the strength of the commodity tank in its role as a support 

structure. Various means of increasing the strength of the tank 

are compared in this section. 

Shell structures (such as aircraft fuselages and ship hulls) 

are often reinforced with ribs; that is, with beams connected 

along their length to the shell. This arrangement increases the 

bending resistance of the shell with little additional weight. 

Ribs may be attached by welding, glue bonding, riveting, or 

they may be formed directly into the shell. Figure 16 illustrates 

a schematic of spider web arrangement of ribs on a tank car 

head. This arrangement is investigated with finite element 

analysis with ribs that have a cross-sectional moment of inertia 

of 12.6 in4

 and a cross-sectional area of 12.6 in2. The head has 

a thickness of 0.777 in. 

Ribs (beams) attached 

to surface of tank head

Figure 16. Tank Head Reinforce with Spiderweb 

Arrangement of Ribs 

Figure 17 shows the deformed shape of the baseline head, 

as well as the deformed shape of the head reinforced with ribs 

for an impact in the center of the head with a blunt punch. The 

figure shows the maximum indentation of both heads when 

they have absorbed 1 million ft-lb of energy. The reinforced 

head has deflected significantly less than the baseline head for 

the same amount of absorbed energy. 

Baseline

Reinforced

Figure 17. Indentations of Baseline and Reinforced Head, 

Center Impact with a Blunt Punch 

Figure 18 shows the force-indentation characteristics for 

the baseline and reinforced heads for an impact in the center of 

the head. The energy required to deform the head is the 

integral of the force-indentation curve. The area under the 

force-indentation characteristic for the reinforced head is more 

than twice the area under the characteristic for the baseline 

head. Figure 18 also shows the force-indentation characteristic 

for a head reinforced by thickening the material to 1.11 in. The 

area under that curve is greater than the area under the baseline 

curve; however, it is significantly less than the area under the 

curve associated with the head reinforced with ribs. 

0

500

1000

1500

2000

0 5 10 15 20

Indentation (in)

Force (kip)

Baseline

Thicker Head

Reinforced Head

Figure 18. Force/Indentation Characteristics, Baseline 

Head, Head Reinforced with Ribs, and Thickened Head, 

Center Impact with a Blunt Punch 

Figure 19 shows the undeformed shaped of the reinforced 

head, as well as the deformed shape after an impact from a 

blunt punch at a location away from the center of the head. 

This location was chosen to be between the reinforcements, 

where they would likely be least effective. Nevertheless, the 

deformed shape suggests that the reinforcements are indeed 

still effective. 

Figure 19. Indentation of Reinforced Head, Offset Impact 

with a Blunt Punch 

Figure 20 shows the force-indentation characteristics for 

the baseline and reinforced heads for an offset impact with a 

blunt punch. The force levels are not as high as for the center 

impact, for both the baseline and reinforced head. However, 

the area under the force-indentation characteristic for the 

reinforced head is again more than twice the area under the 

characteristic for the baseline head. 
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0

500

1000

1500

2000

0 5 10 15 20

Indentation (in)

Force (kip)

Baseline

Reinforced

Figure 20. Force/Indentation Characteristics, Baseline 

Head and Head Reinforced with Ribs, Offset Impact with a 

Blunt Punch 

The head reinforced with ribs can also support an energy 

absorption component that crushes at a higher load than the 

baseline and thickened heads. Alternative means of absorbing 

energy are currently being investigated, including plastic 

foams, aluminum honeycomb, and steel sandwich structures. 

This research suggests that a tank car reinforced with ribs and 

such an energy absorbing structure could maintain tank 

integrity for an impact with four times the energy as the 

baseline tank car. 

SUMMARY AND NEXT STEPS 

Research is being conducted to support the rulemaking 

activities of FRA related to the TIH tank cars. Research results 

to date suggest that an improved design tank car can double the 

car-to-car impact speed for which integrity of the tank is 

maintained over that of conventional tank car designs. 

Reinforcing the head alone can potentially increase the 

maximum impact energy by a factor of 2, increasing the 

maximum containment speed by 50 percent. Results suggest 

that reinforcing the head and adding an energy absorbing layer 

increases the tank integrity energy by four times and doubles 

the maximum containment speed. While not presented in the 

paper, similar results have been obtained for the impact 

resistance of the shell. 

The results of this research are being shared with the 

Dow/Union Pacific/Union Tank Car Next Generation Railroad 

Tank Car. Cooperative activities include the full-scale shell 

impact testing of conventional equipment. As described in a 

companion paper [5], FRA supported the Volpe Center in 

designing these tests and simulating the results of the tests with 

simplified models. Dow Chemical supported Applied Research 

Associates Inc. in conducting simulations of the test using a 

detailed model and supported the Transportation Technology 

Center Inc (TTCI) in implementation of the tests. 

While information is being shared, the design development 

activities supported by Dow Chemical are separate and distinct 

from the design development activities being conducted by the 

Volpe Center in support of FRA. In the process chosen by 

FRA, an overall strategy is evolved into a single concept with 

required functions and features. These features are then refined 

into detailed forms with preliminary design studies. This 

approach has been used to develop crush zones for passenger 

equipment [9, 10, and 11], the state-of-the-art cab car end 

frame design [12], and improved locomotive crashworthiness 

features [15]. Alternative design development approaches 

exist; any of which may result in an improved tank car 

conceptual design that differs from the conceptual design 

described in this paper. The performance achievable with such 

an alternative may exceed the performance associated with the 

conceptual design described in this paper. 

Preliminary design studies are ongoing for the further 

refinement of the conceptual tank car design presented in this 

paper, including ongoing studies of available weight and space, 

strategies for increasing energy absorption, and strategies for 

strengthening the head and shell. Studies on additional design 

details of the sacrificial structures, including means of blunting 

the load, and the carbody structure, are also ongoing. 

In order to achieve the required performance, it is 

necessary to change the size of the tank car. Such changes will 

affect the how the commodity is loaded and unloaded. In 

addition, it is understood that the design must account for 

placement of safety appliances. The details of the final car 

layout will be defined and discussed in future studies. 

Component tests of a head strengthening strategy, as 

discussed in this paper, are tentatively planned to assess the 

results of analyses results for the mode shape and force/dent 

characteristic. Depending on funding, component tests of shell 

strengthening and the sacrificial structure(s) may also be 

conducted. 

ACKNOWLEDGMENTS 

FRA Office of Research and Development sponsored the 

work described in this paper. Ms. Claire Orth is the Chief of 

the Equipment and Operating Practices Division. Mr. 

Francisco Gonzalez is the FRA program manager for research 

on railroad tank cars. 

Mr. Grady Cothen, Deputy Associate Administrator for 

Safety Standards and Program Development, FRA, is leading 

the effort to develop tank car safety standards. Mr. Eloy 

Martinez, FRA program manager, is developing the technical 

information needed to support the FRA and PHMSA 

rulemaking effort. The authors thank Ms. Jo Strang, Associate 

Administrator for Safety Enforcement, FRA, for her efforts to 

coordinate the standards development and the tank car safety 

research. 

The authors also thank Ms. Michelle Priante and Mr. Philip 

Mallon, Mechanical Engineers, Volpe Center, for their efforts 

in developing concepts for improving tank car safety. Dr. 

David Jeong, Senior Engineer, Volpe Center, is leading the 

effort to evaluate the performance of baseline equipment. 

Finally, the authors would like to thank Professor A. Benjamin 
This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for 

public release; distribution is unlimited. 

 10 

Perlman, Senior Engineer, Volpe Center, for his assistance 

through all aspects of this project. 

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